Re: [Qemu-devel] Heads up: glibc preadv emulation breaks qemu on older kernels

[Anthony Liguori <anthony@codemonkey.ws>]

On 02/12/2010 07:50 AM, Christoph Hellwig wrote:
> On Fri, Feb 12, 2010 at 04:49:23PM +0300, malc wrote:
>    
>> On Fri, 12 Feb 2010, Christoph Hellwig wrote:
>>
>>      
>>> On Thu, Feb 11, 2010 at 07:06:08PM +0000, Richard W.M. Jones wrote:
>>>        
>>>> One interesting thing is that qemu has its own preadv emulation (which
>>>> does the emulation correctly), but this is never used because qemu
>>>> never gets ENOSYS back from preadv.
>>>>          
>>> At this point the amount of bugs in the glibc preadv/pwritev code really
>>> make me want to go to use the raw system calls on Linux only.  Any
>>> opinions from the maintainers if that is acceptable?
>>>        
>> There are more than one way to parse the first sentence, if it should be
>> read as:
>>    On linux and on linux only avoid using pread/write[v] and talk to the
>>    kernel directly.
>>
>> Then i agree.
>>      
> Yes.  The BSDs tend to not play stupid emulation games in the libc, so
> changes of these kinds of messups to happen are far less.
>    

In all fairness, I seem to recall there being a problem with the kernel 
implementation of preadv/pwritev too.

I think a configure option would be in order.  Forever avoiding glibc is 
probably a bit extreme.

Regards,

Anthony Liguori

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